The prior art provides ballast circuits for gas discharge lamps of the type including a d.c. to a.c. converter with a pair of serially connected switches whose operation is controlled by self-resonant feedback circuits. A starting circuit is included to initiate self-resonant oscillation of the ballast circuits. This is accomplished by creating a pulse of current through a voltage-breakover (VB) switch, such as a diac, which is accomplished by biasing the VB switch to its threshold voltage for firing (i.e., becoming conductive). During steady state operation of the starting circuit, it is necessary to keep the voltage across the VB switch below its threshold for firing, and one typical circuit to accomplish this includes a p-n diode with its cathode connected to the common node between the mentioned pair of switches. For instance, such a p-n diode is included in the starting circuit disclosed in U.S. Pat. No. 4,353,010.
The cost of the p-n diode used in prior art starting circuits is high relative to the cost of other circuit components, such as resistors. It would, therefore, be desirable to provide a ballast circuit including a starting circuit that did not require a p-n diode for preventing firing of a VB switch during steady state ballast operation.